This is set in the future; humans already achieved Type II civilization status. Humans conquered the entire Solar System and managed to colonize Jupiter and all its moons. The next big challenge is to create an artificial living quarter that is bigger than all spacecrafts and planets.


The objective is to leave for the nearest star, as there is an imminent threat as one of the nearby star is going supernova and the gamma ray burst (GRB) is expected to sweep through the entire Solar System. In order to avoid sterilization from the GRB, man decided to leave for a prolonged journey to the next home.


  1. Spacecraft must not collapse on itself (you are allowed enormous interior space)
  2. Use all available resource within Solar System.
  3. Spacecraft must be assembled within heliosphere.
  4. Transmutation and Magic are not allowed.
  5. Spacecraft must support all lifeforms within Solar System on its
    journey to reach its destination.
  6. Spacecraft's volume must be bigger than Jupiter.
  7. Spacecraft must be ready for interstellar travel.


Is it possible for a spacecraft to dwarf Jupiter? How?


Why the need to dwarf Jupiter, you ask? I believe a warp drive isn't available to a Type II civilization, and journeying at subluminal speed to the nearest star would take numerous generations thus more space less conflict.

You only need to consider the feasibility of implementing/erecting an engineering structure on this scale; ignore artificial climates and ecosystems' designs and their influence.

  • $\begingroup$ Have you seen the Greatship series of stories? That is about the size of Neptune, so your's is bigger. But it's not as large as the "ship star* of Niven and Benford. $\endgroup$
    – JDługosz
    Commented Apr 12, 2015 at 7:08
  • $\begingroup$ How do you get to Type II without building a Dyson Sphere? $\endgroup$
    – AndyD273
    Commented Apr 12, 2015 at 14:43
  • 1
    $\begingroup$ You know that a GRB in a nearby galaxy would have no chance of hurting humanity, right? $\endgroup$
    – HDE 226868
    Commented Apr 12, 2015 at 15:46
  • 1
    $\begingroup$ In order to avoid sterilization from the GRB, man would be much smarter to build deep underground shelters that would allow us to wait out the burst. $\endgroup$
    – SF.
    Commented Apr 12, 2015 at 21:43
  • 2
    $\begingroup$ ...A story in which Edison and the Wright brothers team up to do something incredibly stupid in order to save humanity from impending doom. I like that! $\endgroup$
    – Abulafia
    Commented Apr 13, 2015 at 12:12

4 Answers 4


A Bubbleworld would meet your specifications, especially if you encased Jupiter.


A bubbleworld is an artificial construct that consists of a shell of living space around a sphere of hydrogen gas. The shell contains air, people, houses, furniture, etc. It was invented to answer the question, "What is the largest space colony that can be built?"[24] However, most of the volume is not habitable and there is no power source.

Theoretically, any gas giant could be enclosed in a solid shell; at a certain radius the surface gravity would be terrestrial, and energy could be provided by tapping the thermal energy of the planet.

The shell would hold all of the plants, animals, habitat.


Start by taking apart Mercury, Venus, and Mars, the asteroids, Plutoids, Kupiter belt, and any moons that aren't water. That's your raw construction material.

Habitats can be created as spheres interconnected with tubes, like stringing beads on a wire. A lot of the spheres can be spun for artificial gravity, with the access tubes as the axel. This framework can be built in pieces, first in a ring around Jupiter, and then expand outward until the planet is encased.


Moving something bigger than Jupiter (or Jupiter with a shell around it) is going to take a lot. Gravity manipulation is going to be useful, but if that is too close to magic, then there is another option. Get some really really big drives, call them planetary drives, and put one on the Jupiter bubble, one on Earth, and one on each gas giant. The drives will use the planetary hydrogen as fuel. You need Jupiter for its heat, so avoid using it for fuel. Instead the other gas giants are the fuel tanks. They will provide the fuel to accelerate themselves, as well as provide the fuel for Earth and the Jupiter bubble.

As each gas giant runs out of atmosphere, the cores can be mined for metals and anything left is just set adrift.

You surround earth with orbiting fusion furnaces, which would keep it from freezing, and put it in orbit around Jupiter, along any ice/water moons you have. Jupiter's magnetic field will help protect Earth and the shell from interstellar radiation.

  • 1
    $\begingroup$ +1 bringing Jupiter along how nice to keep a memento for reminiscent. $\endgroup$
    – user6760
    Commented Apr 13, 2015 at 0:08
  • 1
    $\begingroup$ Jupiter is important, heat, fuel, power. Not sure if you meant earth? Honestly it's mostly because it would be hard to recreate the habitats to get the right biodiversity. It would basically be a park probably $\endgroup$
    – AndyD273
    Commented Apr 13, 2015 at 0:16
  • $\begingroup$ Actually, you wouldn't need to spin the spheres. I missed the part where you just put the shell at the right altitude above the gas giant where the gravity from the planet would feel earth normal. $\endgroup$
    – AndyD273
    Commented Apr 13, 2015 at 1:39
  • $\begingroup$ Even when just building a thin shell, will there be enough materials? Jupiter is 65% of the mass of the solar system (ignoring the sun) and it's a cloud of gas. Encasing it in anything solid would require insane amounts of material. There might simply not be enough rock available. $\endgroup$
    – Erik
    Commented Apr 16, 2015 at 6:39
  • $\begingroup$ @Erik that's a fair point, and I don't know if I can answer it, but I am willing to bet that a lit of Jupiter's mas is in its core, which is some kind of metal I think. Might help. $\endgroup$
    – AndyD273
    Commented Apr 16, 2015 at 11:20

I'm a bit curious as to why they would want to build a singular object larger than Jupiter to travel to the new star when they could achieve the same results for a fraction of the time and effort by building billions of really large spaceships.

With our own technology, an "Island 3" colony 8km in diameter and 30km long can be built; ensure they have efficient closed cycle ecologies and a long lasting power supply for the interstellar journey and we are ready to go. Colonies would be built with different internal biospheres depending on what you actually want to transport.

A Bishop Ring could be built using carbon nanotubes. It theoretically has a 1000km radius and a floor 500km across, with the atmosphere contained by a wall of mountains on the edges over 120km high, giving a surface area roughly the size of India. For interstellar journeys it would need to be roofed over for thermal control. Once again, billions of these could be built with a multitude of biospheres (including entirely arbitrary and "artificial" biospheres that a Type II civilization makes for entertainment or hobby purposes).

The key advantage is the time and resource cost for building each individual colony/starship is much less than building a Jupiter sized mega structure, and a stream of ships could be launched over an extended period of time. As well, since each ship is self contained, there would be no issues of a fault or failure on one ship giving rise to a cascade failure that wipes out the entire fleet. A cascade failure on a Jovian sized structure could theoretically cause the extinction of the entire population of the Solar System if it is carrying everyone and everything.

And of course the arrival of a billion "Bishop rings" in the new star system would be an amazingly impressive sight, more so as they settle into solar orbit around the new sun


Recently, there was an interesting article about Kardashev Type II Civilizations, Dyson Spheres, and the Fermi Paradox.

White Dwarf Dyson Sphere
In summary, build your sphere around a white dwarf star. It provides many advantages:

  • Requires fewer material (only about the mass of 1-2 terrestrial planets)
  • Is smaller
  • Live on the outside of the sphere at 1g
  • Leave an opening and the star is your engine, the port is the nozzle
  • It is much cooler than the Dyson Spheres we have been looking for

You could light the surface by using clear viewports and then reflect the light back onto the surface.

This structure would be about 1 million miles in diameter. It would dwarf Jupiter - being about 10-20 times larger.

Other possibilities
You could do the same thing with the same sized sphere around a gas giant. Unfortunately, it suffers from some drawbacks.

  1. Gravity at the surface of this sphere would be significantly less than 1 g.
  2. Power output by the body would be much less than that of a whitedwarf.
  3. Even with strategically placed holes, this construct could not move itself.

Look at some of Greg Egan's work. As hard-sf, there is no warp drive, but he tends to have people beaming around the galaxy at lightspeed.

If your civilisation can colonize Jupiter, they are clearly not limited to human biology. It would not be limited in the ways you otherwise imply.

A GRB in a another galaxy? Do you understand how far away that is? (1) it is unreasonable thatnit would be aimed right at us from so far away, and (2) would it be dangerous over such a long distance?

I think if a type II civilization detected that such a burst would happen ahead of time (and I do find that reasonable: they will have telecopes of awsome size and separated by billions of miles with interferometry combining of signals), they would put a shield up to block it. Not only shade themselves, but harvest the power of gamma and neutrino flux to transmute elements and drive experiments.

You need a different excuse. How about "because it's there"?

A spaceship that big, with the mass of at least a small planet, will be a beast to move. How would you power it? The type II civilisation is already using all the energy from the sun: what's it used for normally, and how will this construction project affect the budget?

Where would you get materials to make it? A light framework could be made from carbon fiber, but a scaffold that big will use a lot of material that is not hydrogen. If the intent is to cover it over with a skin, why bother? If it's to shield the inside against debris when moving at high speed, is there enough stuff and boy will it be heavy (see above) so you won't have to worry about high speed after all. :)

It might use a magnetic shield like a planet. Then the framework can remain light, to keep individual habitats and other bodies tethered and mark the edge of the safe zone. You could take some moons and small, planets with you. If you could get enough energy to thrust them.

You might have to break from hard sf and postulate a gravitational warp of some kind. It won't provide superluminal travel, but it could keep all the stuff in your huge sphere together in a field, so that the inside does not feel thrust and all moves along with the container, and furthermore moves space itself to avoid classic newtonian thrust. You could require the great size as part of what makes it work, and require ballast of planetary masses as well.


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